Approximately 26 percent of the world's land area – including one-third of tropical and temperate forests, and a quarter of natural grasslands – have been converted for the use of agriculture and livestock. And scientists estimate that currently, annual conversion of wild lands for agriculture continues to reduce 1.5 percent of the total rain forest on earth.

These staggering figures demonstrate how significant an impact human food consumption and farming practices are having on wildlife habitat. But while some types of farming and grazing practices are less harmful than others, certain types of agricultural clearing methods such as "slash and burn" or "shifting cultivation" are being used in inappropriate climates resulting in highly unsustainable farming efforts and significant losses to biodiversity.

These methods of land clearing burn down forests to create new fields for agriculture. However, in tropical climates, the nutrients from the burns can only sustain healthy crop yields for a limited time before the farmers are forced to burn more forest and start over on a new piece of fertile land.

Although slash and burn agriculture has been found inefficient and destructive for large populations in tropical areas, the process is still frequently practiced.

On the island country of Madagascar, Africa, the continued use of slash and burn clear-cutting is speeding up erosion processes and eating away jungle forests that provide the only known homes for many species of lemurs.

Slash and burn agriculture is the process of cutting down the vegetation in a particular plot of land, setting fire to the remaining foliage, and using the ashes to provide nutrients to the soil for use of planting food crops. Slash-and-burn is an agricultural technique which involves cutting and burning of forests or woodlands to create fields. It is subsistence agriculture that typically uses little technology or other tools. Slash-and-burn techniques are used by between 200 and 500 million people worldwide. In 2004 it was estimated that, in Brazil alone, 500,000 small farmers were each clearing an average of one hectare of forest per year. The technique is not sustainable beyond a certain population density because, without the trees, the soil quality soon becomes too poor to support crops. The farmers have to move on to a virgin forest and repeat the process.

The cleared area following slash and burn, also known as swidden, is used for a relatively short period of time, and then left alone for a longer period of time so that vegetation can grow again. For this reason, this type of agriculture is also known as shifting cultivation

Negative Aspects of Slash and Burn

Many critics claim that slash and burn agriculture contributes to a number of reoccurring problems specific to the environment. They include:

• Deforestation: When practiced by large populations, or when fields are not given sufficient time for vegetation to grow back, there is a temporary or permanent loss of forest cover.
• Erosion: When fields are slashed, burned, and cultivated next to each other in rapid succession, roots and temporary water storages are lost and unable to prevent nutrients from leaving the area permanently.
• Nutrient Loss: For the same reasons, fields may gradually lose the fertility they once had. The result may be desertification, a situation in which land is infertile and unable to support growth of any kind.
• Biodiversity Loss: When plots of land area cleared, the various plants and animals that lived there are swept away. If a particular area is the only one that holds a particular species, slashing and burning could result in extinction for that species. Because slash and burn agriculture is often practiced in tropical regions where biodiversity is extremely high, endangerment and extinction may be magnified.